Core-retrieving method and apparatus

ABSTRACT

Apparatus for retrieving cores while drilling a borehole which enables an elongated cylindrical solid core sample to be obtained from a formation. A coring bit together with a core barrel which remains stationary with respect to the core being cut enables the core to be broken into predetermined lengths and circulated uphole to where the core is captured within a core retriever made in accordance with the present invention, and which enables the intact core to be removed from the drill string.

United States Patent Wayland D. Elenburg P.0. Box 1588, Monahans, Tex. 79756 831,361

June 9, 1969 Continuation-impart of application Ser. No. 714,551, Mar. 20, 1968, now Patent No. 3,473,6 17.

Inventor Appl. No. Filed Patented CORE-RETRIEVING METHOD AND APPARATUS 8 Claims, 8 Drawing Figs.

U.S. Cl 175/255, 175/60, 175/308 1nt.Cl E2115 9/20, E2lb 25/00 Field 01 Search 175/246, 250, 255, 214

[56] References Cited UNlTED STATES PATENTS 2,671,642 3/1954 Stokes 175/255 2,708,104 5/1955 McAllister.... 175/255 3,208,539 9/1965 Henderson... 175/215 3,338,322 8/1967 Henderson 175/21sx Primary Examiner-Ernest R. Purser Assistant Examiner-Richard E. Favreau Attorney-Marcus L. Bates ABSTRACT: Apparatus for retrieving cores while drilling a borehole which enables an elongated cylindrical solid core sample to be obtained from a formation. A coring bit together with a core barrel which remains stationary with respect to the core being cut enables the core to be broken into predetermined lengths and circulated uphole to where the core is ceptured within a core retriever made in accordance with the present invention and which enables the intact core to be removed from the drill string.

Patented Aug. 3, 1971 3 Sheets-Sheet 1 lA vlnw'ok WAYLAND D. ELENBURG MARCUS L. BATES Patented Aug. 3, 1971 3,596,723

3 Sheets-Sheet INVENTOR. WAYLAND O. ELENBURG BY MARCUS L. BATES .II .II I

3 Sheets-Sheet I Patented Aug. 3, 1971 l llllll llllll II HWII IIIII W T 6 6 M w M 7 &% VRKQ Q l. i aw.

INVIZN'I'OR.

WAYLAND D. ELENBURG MARCUS L. BATES CORE-RETRIEVING METHOD AND APPARATUS BACKGROUND OF THE INVENTION Reference is made to my U.S. Pat. No. 3,439,757, issued Apr. 22, 1969, and to the above U.S. Pat. No. 3,473,617 for background of the present invention. In carrying out drilling operations according to my previous patent and patent application, it has been found that passage of a solid core sample through the conventional gooseneck of a coring rig causes substantial damage to the core and it is therefore desirable to be able to obtain a core intact from the formation so as to receive a more representative sample of the material which forms the borehole. Moreover, it is desirable to be able to obtain undamaged core samples which are of a much longer length than is presently possible using conventional coring and retrieving apparatus. It is also desirable to be able to achieve cores of a predetermined length by manipulation of the drill string which in turn breaks the cores into an arbitrary length.

SUMMARY OF THE INVENTION The present invention comprehends both method and apparatus for carrying out an improved boring, coring, and retrieving operation while fonning a borehole, and specifically related to method and apparatus for obtaining undamaged lengths of cores from the bottom of a borehole. concentrically arranged pipe forming a drill string having a central and annular passageway formed therein for circulating fluid to the bit and for providing a return flow path for obtaining the core is suitably connected to a core cutting bit by a combination sub and core barrel. A core-retriever assembly is interposed in series relationship within the inner tubing at a location near the kelly. Drilling fluid is forced down through the annulus of the drill pipe or drill string and into close proximity of the cutting teeth of the bit, causing fluid to be forced either back up through the hole annulus or up through the inner tubing, as may be desired. A core barrel attached in journaled relationship to the drill bit is maintained stationary with respect to the core being cut. A core catcher cooperates with the core and core barrel in a manner to maintain the core barrel in a nonrotating condition with respect to the core being cut. When it is desired to break the partially formed core from the formation, the drill string is elevated, whereupon the core is broken away from the formation and circulated up hole by drilling fluid. The core travels up hole within the inner tubing and is captured within a core retriever. If desired, an identical core retriever can be substituted for the one which contains the cut core in order to enable the drilling operation to be immediately resumed with little interruption thereof.

It is therefore a primary object of the present invention to provide a method of obtaining core sampled from a borehole by forming elongated cores and circulating the cores back to the surface of the earth by an improved flow pattern.

Another object of the present invention is the provision of apparatus for retrieving intact elongated cores during a core drilling operation.

A further object of the present invention is the provision of a stationary core barrel which is maintained in nonrotating condition with respect'to the core and which includes an improved core catcher, core breaker, and means for maintaining the core barrel stationary with with respect to the core being cut.

A still further object of the present invention is the provision of a core retriever assembly for use in conjunction with a nonrotating core barrel.

The above objects are attained in accordance with the present invention by the provision of concentrically arranged drill pipe which are connected to a bit, to a nonrotating core barrel, and to a core-retrieving assembly, all of which cooperate together to provide an improved means by which cores may be obtained from the interior of the earth.

These and other objects of the present inventionwill become apparent to those skilled in theart as the description of the invention proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatical cross-sectional representation of the earth's structure with the present well-boring apparatus being operatively positioned therein in order to broadly explain the operation of the present invention;

FIG. 2 is an enlarged cross-sectional view of part of the apparatus seen in FIG. 1;

FIG. 3 is an enlarged fragmentary cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an enlarged fragmentary crosssectional view taken along line 4-4 of FIG. 2;

FIG. 5 is an enlarged cross-sectional view of part ofthe ap paratus disclosed in FIG. 1, with parts thereof being broken away from one another and connected by dot-dashed lines in order to better illustrate the invention; and

FIGS. 6, 7, and 8, respectively, are cross-sectional views taken along lines 6, 7, and 8 respectively, of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 schematically sets forth a portion of a well-drilling apparatus 10 which is in the act of boring a hole into the earth's structure. Part of the apparatus is located above the surface 11 of the earth, while the remainder of the apparatus is located down hole in the usual manner. Circulation of drilling fluid is accomplished by means of swivel 12, the details of which are known in the art, with fluid flow occurring to and from the apparatus as indicated by the arrows at numeral 13. A kelly 14 is rotated by conventional means, not shown. A core retriever 16, made in accordance with the present invention and having upper and lower inner tubing connection means 18, 19, respectively, is concentrically received within drill string 20 which is made up of a multiplicity of drill pipe joints 22.

Connected to uppermost inner tubing joint 24 is a multiplicity of inner tubings 24 which extend down hole at 24" to a core barrel. The inside peripheral wall surface of the drill pipe or drill collar, which ever may be used, is seen at 25. A drill bit 26 has a core receiving annulus 28 which is of a size to enable core barrel 30 to receive core 32 therein as the core is being formed. Spaced apart guide means 33 maintains the core barrel aligned within the lower depending end of the string, all in a manner as described in my before identified patent application.

Looking now to FIG. 2, an enlarged cross-sectional view of the before mentioned outer and inner barrel and bit are shown in detail. It should be understood that the device of FIG. 2 is connected to the drill string and related apparatus of H6. 1. The annulus formed between the inner and outer tubing provides an annular passageway 44 with the core barrel being attached to the sub by means of a bearing such as seen at as. A collar 43 threadedly engages the core barrel in a manner to capture the bearing therebetween as illustrated at 59. The central portion 52 of the barrel extends downwardly to where it threadedly engages member 54, the depending end of which forms a shoulder at 55.

Threadedly attached to the lower terminal end of the corebreaker member is a cylindrical downwardly converging corecatcher housing 63 having a key 62 thereon, and which includes vertically spaced apart splines thereon (not shown) which cooperate with similar spaced apart splines; provided on the outside peripheral wall surface of the inverted frustoconical core catcher and breaker 64, the details of which are best seen in FIG. 3. The lower terminal end portion of the core barrel terminates at 61. The inside face of the drill bit is provided with grooves 67, having a bottornmost portion es, to thereby leave a passageway between the lower terminal end of 2 3 inner barrel and the inside of the bit.

The'face of the bit containing the diamonds is generally seen at 66, with the lower inside portion of the it be? girovided with the before-mentioned grooves which permit the passage of fluid to be forcibly bent across the inside peripheral portion 69'which forms the central aperture of the bit. Accordingly, a passageway 7% is formed between the outer peripheral surface of the various members which forms the core barrel and the inside peripheral wall surface of the outer barrel. The passageway continues as seen at 73 to where it branches into a multiplicity of radially spaced apart passageways 74 which are drilled through the before-mentioned sub 42 so as to communicate at 75 with the annular passageway formed by the drill string.

FIG. 5, in conjunction with FIGS. 6, 7, and 8, sets forth the details of the before-mentioned core retriever generally illustrated at 16 in FIG. 1. Sub 76 is series connected at 18, 19 and forms a part of the drill string. The inside peripheral wall of the sub downwardly diverges at 77 to form chamber 77'. The upper end of the sub is counterbored to form a shoulder 78 located between inlet 18' and the beforementioned chamber.

Outer peripheral wall surface 79 of the core retriever cooperates with the inside peripheral wall surface of the drill pipe sub to form annulus 80. Upper connection 18 is provided with cross 82 which forms a core abutment means therein. Circumferentially extending seal means 83 enables the upper marginal end portion of the retriever to be telescopingly received in sealed relationship within the upper connection. Enlargement 85 includes upper and lower opposed shoulders, the lower one of which is abuttingly received against the before-mentioned shoulder 78. Optionally provided between the enlargement and the chamber is a downwardly and outwardly diverging portion 86 which terminates in the illustrated circumferentially extending edge portion for facilitating removal of the retriever. Intermediate the depending ends of the retriever there is provided a second core catcher housing 87 having a downwardly depending threaded skirt at 87' which threadedly engages lower portion 89 of the retriever, with the housing enclosing the second core-catcher assembly generally illustrated by the arrow at numeral 88.

Radially spaced apart guide means 89' are slidably received by the inside peripheral wall 90 of the sub so as to maintain the lower end portion of the retriever centrally aligned with respect to the drill pipe sub.

The core catcher assembly 88 includes the illustrated spaced apart cages 91 which are received within recesses provided within the housing. A plurality of individual fingers 92 are provided and are pivotally attached to the cages by pin 93. The fingers may be rotated from the core-catching position at 92 to the core passing or retracted dot-dashed line position seen at 92'. A spring biasing means (not shown) can be included for urging the fingers into the closed position, if desired.

Annulus 93' is formed between the outer wall of the upper connection and the inside wall surface of the drill pipe. Radially spaced apart ports 94 are in fluid communication with annulus 93' and 95. The second core catcher housing is spaced apart from chamber 77' to form annular flow path 96 therethrough. Between guide means 89 there is provided several flow passageways 97, while the lower female connection is spaced apart from the pin or male connection of the drill pipe so as to provide an annular passageway 98 which is aligned with the annulus formed between the inner tubing and the drill pipe.

OPERATION In operation the swivel supports the drill string in a conventional manner with drilling fluid flowing to and from the bit by means of passageways at 13. The kelly imparts rotational motion into the bit in the usual manner. The fluid flow path can be traced from the swivel, through the annulus between the uppermost joint of the inner tubing and the kelly, through annulus 93, ports 94, annulus 95, annular chamber 96, passageways 97, annulus 98, down the drill string annulus and around the lower barrel at 44 where the fluid is available for cleaning, washing, and cooling the drill bit. The flow can now return to the surface by means of the hole annulus or alternatively, it can flow up through the inner tubing, depending upon the controlled hydrostatic condition of the particular boring operation as previously explained in my copending patent application.

As core 32 is formed or received within the core barrel the lowermost end of the core remains attached to the formation with the sidewalls of the core being telescopingly received in close-fitting engagement by the lower core catcher so as to maintain the core barrel in a nonrotating condition; that is, the barrel is held stationary with respect to the formation. When a core of a desired length has been attained by the cutting action of the bit, for example, a three foot core sample, the drill string is lifted by means of the swivel. This action causes the lower core catcher to squeezingly engage the core with an increasing force due to the action of the core catcher with respect to its housing which forces the core catcher to assume a smaller diameter. Stated differently, the core catcher is forced downward against the sloped wall of its housing, causing an increased force to be exerted against the core while at the same time the upward movement of the drill pipe exerts an upward force upon the core sample, thereby breaking the lower end of the core away from the formation. After the core sample has been pulled apart from the formation it will be realized that the core is now held within the core catcher and barrel. The drill bit is again set down and several additional inches of formation penetration is made in order to commence forming a new core, the upper extremity of which pushes the previously cut core sample out of the core catcher and into the core barrel.

The freed core sample is now a free body analogous to a piston which is reciprocatingly received within a cylinder. As the drilling operation continues, the pressure differential of drilling fluid across the freed core sample enables circulation of the core up hole.

Circulation of drilling fluid forces the core up hole through the inner tubing where it must eventually enter the core retriever and contact the abutment means or cross 82, thereby causing the core to be captured within the core retriever. As the core sample enters the lower portion of the core retriever, fingers 92 are pivoted from the illustrated position seen at 92 into the dot-dashed position seen at 92'. As the lower end portion of the core sample passes clear of the upper core catcher, the fingers return to the illustrated position seen at 92. Where deemed desirable, each of the fingers may be spring loaded or biased into the horizontal or core-catching position 92.

As the core abuts the cross 82 a pronounced increase in the drilling fluid pressure indicates that the core has arrived within the core retriever or receiver, whereupon the kelly is picked up by the swivel, set down on a set of slips located within a conventional bowl, and the sub 76 is then disengaged from the kelly at 18', thereby enabling the inner tubing to be broken at upper connection 18 so as to enable the core retriever to be removed from the sub. The upper connection is removed and the core sample is emptied into a tray by merely inverting the retriever, after which it is assembled and replaced within the sub, the upper connection made back up, the i-zelly SCX'C. we. back onto the upper connection 18', whereupon the siips an. removed, the bit set back on bottom, and drilling recommenced in order iZO cut and obtain the next core section.

Where deemed desirable, an extra sub having a core retriever therein can be substituted for the sub and retriever which contains the core sample, thereby gaining a few seconds time and enabling the core sample to be removed from the core retriever in a more leisure manner.

it is pointed out that the lower core catcher iii-1i serves three different purposes, that is, as a lower core catcher, a core breaker, and as a means for maintaining the lower core barrel in a nonrotating condition relative to the formation being penetrated. The core catcher can be ribbed er spiined as seen in FIG. 2, or alternatively, it can be provided with an inside peripheral wall surface comprised of highly abrasive particles such as realized by brazing or otherwise surfacing the catcher with tungsten carbide particles or the like.

The location of the sub which contains the retriever is not considered critical so long as it is interposed within the drill string at a position which permits access thereto during the drilling operation. Furthermore, those skilled in the art will realize that several different circulation patterns can be carried out while using the present invention, as for example, the return fluid can flow up the hole annulus, up the inner tubing, or a combination of both.

The maximum core length attainable with the present invention is determined by the length of the core retriever and to some extent by the length of the core barrel. However, it is preferred to cut cores slightly more than three feet in length because a core of this length provides adequate pressure drop thereacross in order to develop sufficient force to cause the core to travel up hole to where it is captured within the core retriever.

I claim:

1. In a well-drilling apparatus having a rotatable drill bit for cutting cores from formations, with the bit being connected to a drill string which is comprised of concentrically arranged drill pipe and inner tubing to form a central and annular passageway for countercurrent flow therethrough, and wherein said bit has a central aperture therein for receiving cores therethrough with the central aperture including means by which it is flow connected to the inner tubing of the drill string for enabling cores to be circulated up hole therethrough, in combination:

a core barrel having an inside passageway longitudinally aligned with the bit annulus and the inner tubing, means by which said barrel is supported by the drill string, said barrel having means forming an inside peripheral wall portion in the form of an inverted frusto cone which forms a core catcher housing, a core catcher having an outer wall portion in the form of a frusto cone, said core catcher being reciprocatingly received within said corecatcher housing; means associated with said core catcher and said core-catcher housing for preventing relative rotation therebetween; whereby:

said core-catcher can engage and break a core when the core barrel is lifted by the drill string,

2. The combination of claim 1 wherein said core barrel includes means by which it rotatably mounts with respect to the bit, to thereby enable a core which is being cut by the bit to be held stationary by the core catcher.

3. The combination of claim 2 and further including a sub, the bit being attached to said sub, said means by which said core barrel is rotatably secured to said drill string includes a journal between said sub and said barrel; and

said core catcher having abrasive means on the inside peripheral wall surface thereof for securing said barrel to the core to thereby prevent the stated relative rotation thereof.

4. The combination of claim 1 wherein said core catcher is located at the lower'rnarginal edge portion of the barrel for breaking the core in to lengths which are several times greater than the diameter thereof so as to enable the cores tobe circulated up through the inner tubing.

5. The combination of claim 4 wherein said core catcher is a discontinuous circular member which upwardly and outwardly depends from a sidewall of the core catcher housing to thereby cause the core catcher to be reduced in diameter when it travels downwardly within the core-catcher housing.

6. In combination with well-drilling apparatus having a drill string which includes concentrically arranged drill pipe and inner tubing for circulating drilling fluid to and from a formation cutting bit, with the bit having a central passageway for receiving cores therethrough, a core barrel;

said core barrel being interposed between the bit and inner tubing and having means forming a longitudinally disposed inside passage which is aligned with the inner tubing and the central passageway of the bit so as to enable a core cut by the bit to travel through the central passageway of the bit into the longitudinal passageway of he core barrel, and through the inner tubing towards the surface of the earth;

a sub; means by which said barrel is rotationally disposed within said sub so as to form an annulus therebetween to thereby enable concentric countercurrent flow of drilling fluid to and from the bit;

said sub having means associated therewith for connecting the bit to the drill string;

a core catcher, means by which said core catcher can be radially expanded; means by which a portion of the inside peripheral wall surface of said core barrel is formed into a core catcher housing; means by which said core catcher is reciprocatingly disposed within said housing and adapted to enable cores to slidably pass therethrough when reciprocated to an upper position with respect to said housing; said core catcher adapted to engage and break a core away from a formation when said core catcher is reciprocated to a lower position with respect to said hous ing, whereby:

said core catcher can be reciprocated into a position which can engage and break a core when the sub is lifted by an upward movement of the drill string.

7. The combination of claim 6 wherein said barrel is of a length which is several times its innermost diameter and said core catcher is located at the lower marginal edge portion of the barrel to enable breaking the core into lengths which are several times greater than the diameter thereof so as to enable the cores to be circulated up through the inner tubing;

means forming said core catcher into a discontinuous circular member which upwardly and outwardly depends from a sidewall of the core-catcher housing to thereby cause the core catcher to be reduced in diameter when it travels downwardly within the core catcher housing.

8. The combination of claim 6 wherein said core catcher housing is in the form of an inverted frusto cone and said core catcher has an outside wall area which is complementary with respect to the inside wall of said housing, whereby, reciproca tion of the core catcher with respect to the housing causes the recited radial expansion of the core catcher. 

1. In a well-drilling apparatus having a rotatable drill bit for cutting cores from formations, with the bit being connected to a drill string which is comprised of concentrically arranged drill pipe and inner tubing to form a central and annular passageway for countercurrent flow therethrough, and wherein said bit has a central aperture therein for receiving cores therethrough with the central aperture including means by which it is flow connected to the inner tubing of the drill string for enabling cores to be circulated up hole therethrough, in combination: a core barrel having an inside passageway longitudinally aligned with the bit annulus and the inner tubing, means by which said barrel is supported by the drill string, said barrel having means forming an inside peripheral wall portion in the form of an inverted frusto cone which forms a core catcher housing, a core catcher having an outer wall portion in the form of a frusto cone, said core catcher being reciprocatingly received within said core-catcher housing; means associated with said core catcher and said core-catcher housing for preventing relative rotation therebetween; whereby: said core-catcher can engage and break a core when the core barrel is lifted by the drill string.
 2. The combination of claim 1 wherein said core barrel includes means by which it rotatably mounts with respect to the bit, to thereby enable a core which is being cut by the bit to be held stationary by the core catcher.
 3. The combination of claim 2 and further including a sub, the bit being atTached to said sub, said means by which said core barrel is rotatably secured to said drill string includes a journal between said sub and said barrel; and said core catcher having abrasive means on the inside peripheral wall surface thereof for securing said barrel to the core to thereby prevent the stated relative rotation thereof.
 4. The combination of claim 1 wherein said core catcher is located at the lower marginal edge portion of the barrel for breaking the core into lengths which are several times greater than the diameter thereof so as to enable the cores to be circulated up through the inner tubing.
 5. The combination of claim 4 wherein said core catcher is a discontinuous circular member which upwardly and outwardly depends from a sidewall of the core catcher housing to thereby cause the core catcher to be reduced in diameter when it travels downwardly within the core-catcher housing.
 6. In combination with well-drilling apparatus having a drill string which includes concentrically arranged drill pipe and inner tubing for circulating drilling fluid to and from a formation cutting bit, with the bit having a central passageway for receiving cores therethrough, a core barrel; said core barrel being interposed between the bit and inner tubing and having means forming a longitudinally disposed inside passage which is aligned with the inner tubing and the central passageway of the bit so as to enable a core cut by the bit to travel through the central passageway of the bit, into the longitudinal passageway of the core barrel, and through the inner tubing towards the surface of the earth; a sub; means by which said barrel is rotationally disposed within said sub so as to form an annulus therebetween to thereby enable concentric countercurrent flow of drilling fluid to and from the bit; said sub having means associated therewith for connecting the bit to the drill string; a core catcher, means by which said core catcher can be radially expanded; means by which a portion of the inside peripheral wall surface of said core barrel is formed into a core catcher housing; means by which said core catcher is reciprocatingly disposed within said housing and adapted to enable cores to slidably pass therethrough when reciprocated to an upper position with respect to said housing; said core catcher adapted to engage and break a core away from a formation when said core catcher is reciprocated to a lower position with respect to said housing, whereby: said core catcher can be reciprocated into a position which can engage and break a core when the sub is lifted by an upward movement of the drill string.
 7. The combination of claim 6 wherein said barrel is of a length which is several times its innermost diameter and said core catcher is located at the lower marginal edge portion of the barrel to enable breaking the core into lengths which are several times greater than the diameter thereof so as to enable the cores to be circulated up through the inner tubing; means forming said core catcher into a discontinuous circular member which upwardly and outwardly depends from a sidewall of the core-catcher housing to thereby cause the core catcher to be reduced in diameter when it travels downwardly within the core catcher housing.
 8. The combination of claim 6 wherein said core catcher housing is in the form of an inverted frusto cone and said core catcher has an outside wall area which is complementary with respect to the inside wall of said housing, whereby, reciprocation of the core catcher with respect to the housing causes the recited radial expansion of the core catcher. 